Ronald Charles Grant, 10th Baron de Longueuil (13 March 1888 – 12 July 1959) was a British soldier and peer. He was born in Pau, France,[1] the son of John Moore Charles de Bienville Grant. He married Ernestine Hester Maud Bowes-Lyon, daughter of the Hon. Ernest Bowes-Lyon and Isobel Hester Drummond, on 4 October 1918.[1] He was educated at Elizabeth College, Guernsey.[1] He was in the French Foreign Legion and was a civil engineer.[1]
He succeeded to the title of Baron de Longueuil on 17 October 1935.[1] He fought in the Second World War as an officer in the service of the 3rd Battalion, King's Own Yorkshire Light Infantry.[1] He died in Navarrenx, France in 1959.[2]